Petrogenesis Of Granites Research Articles

U-Pb geochronology of the Silurian-Devonian Bega Batholith, south-eastern Australia: Insights into the origin and development of I-type granites

Earth’s continental crust is primarily composed of buoyant, felsic igneous (granitic) material that has been extracted from the mantle along convergent plate margins. Establishing the timescales of subduction-related granite batholith assembly is key to understanding the processes of magma generation, segregation, and transport that define the dynamics and rates of crustal growth. The ‘Cordilleran’ Bega Batholith is the largest I-type granite batholith in the Lachlan Fold Belt (LFB) of south-eastern Australia. The product of accretionary orogenesis along the Terra Australis Orogen, it has been extensively characterised by isotopic and geochemical studies yet lacks a robust geochronological framework. We present new ID-TIMS and SHRIMP U-Pb zircon ages for twenty-two plutonic rocks of the Bega Batholith. This geochronological survey indicates a prolonged duration for I-type magmatism, with crystallisation ages ranging from ca. 420 Ma in the west, to 385 Ma in the eastern Bega Batholith. These I-type granites collectively occupy ∼90,000 km3 and were emplaced over a period of ∼20–35 Ma, corresponding to a magma production rate of ∼8–15 km3/Ma km−1, considerably lower than that of S-type granites of the region and other subduction-related granite terranes globally. Fundamentally, the temporal overlap between the Bega I-type granites and S- and A-type granites also argues against a hiatus between each phase of granite magmatism in the LFB, suggesting a continuum between the granite types and derivation from common source components. This new geochronological data provides the first comprehensive compilation of U-Pb ages from across the Bega Batholith, establishing initial constraints on the development and evolution of I-type magmatism in south-eastern Australia. Our results demonstrate that I-type granite petrogenesis is linked with crustal growth processes, requiring the modification of global crustal growth curves during the Phanerozoic to account for new continental crust generated within I-type granite terranes of the Paleo-Pacific Gondwanan margin.

Petrogenesis of neoproterozoic Mo-bearing A-type granites in the Gattar area, northern Eastern Desert, Egypt: Implications for magmatic evolution and mineralization processes

Three Mo-bearing granitic intrusions, namely: Gattar, Abu Harba and Abu Marwa occur at the Gattar area in the North Eastern Desert of Egypt. These late tectonic granites intrude Neoproterozoic rocks of island arc metavolcanics and metagabbro-diorite complexes in addition to post-collision molasse-type sediments (Hammamat Group) and Dokhan-type volcanic rocks. U–Pb zircon geochronology yielded ages of 630 ± 27 Ma, 600.1 ± 8.5 Ma, and 601.1 ± 2.4 Ma for the Gattar, Abu Harba, and Abu Marwa granite intrusions, respectively.Whole-rock geochemical data showed the granites to be alkaline to peralkaline post-collision A-type granites. The three granite intrusions are considered co-magmatic as indicated by their similar ages and the continuous variation of major and trace elements on the variation diagrams. The inferred crystallization temperatures, as calculated from zircon geothermometry according to Watson et al. (2006), fall in the range of 616–690 °C, (average = 662 °C), 592–720 °C, (average = 653 °C), and 592–894 °C, (average = 706 °C) for the Gattar, Abu Harba, and Abu Marwa granite intrusions, respectively. This indicates that the Abu Marwa granite is the least evolved, followed by the Gattar and Abu Harba granites. The calculated logfO2 values for zircons from all the studied granites show highly oxidized magmatic features. The Abu Marwa granite (average logfO2 = −12.62) has the strongest oxidized state, whereas Gattar granite (average logfO2 is −15.46) and Abu Harba granite (average logfO2 = −15.99) have moderate logfO2 values implying moderate oxidized states. Guided by the tectonic evolution of the post-collision stage in the Arabian-Nubian Shield, it is suggested that the original magma of the granites in the Gattar area was formed by partial melting of an underplated crustal source, which had been fertilized by alkali-, HFSE-, and REE-rich fluids released and metasomatized by an underplating mantle-derived magma.Fractional crystallization and fluid differentiation/metasomatism were major processes in the petrogenetic evolution of these granite intrusions. Fluorine-complexing of HFSEs and REEs was involved in the early stages of fractional crystallization (i.e., crystallization of the Abu Marwa granite intrusion), resulting in a HFSE- and REE-rich residual melt that form the more evolved alkali feldspar granite of Gattar and Abu Harba intrusions. The late magmatic ore-forming fluids enhance the Gattar granite intrusion’s ability to become enriched in molybdenum relative to Abu Harba and Abu Marwa granites. The reason of the different degrees of molybdenite enrichment in the three intrusions depended on many factors (e.g., degree of fractionation and oxygen fugacity of the granitic magma).

Petrogenesis and tectonic implications of Late Permian S-type granites in the South Kunlun Belt, northern Tibetan Plateau

• Two-mica granites in south Kunlun are identified as S-type with ages of 260–257 Ma. • These S-type granites were derived by H 2 O-fluxed biotite melting of metagreywacke . • These S-type granites and their genesis indicate anatexis of an accretionary wedge. S-type granites are striking products of supracrustal reworking and can provide crucial constraints on the anatexis of accretionary wedges in an accretionary orogen. In this study, we present new zircon and monazite dating results, whole-rock geochemistry, and zircon Lu-Hf isotopic data for the two-mica granites in the Muztagh area of the South Kunlun Belt. Integrated dating results reveal that the two-mica granites crystallized at 260–257 Ma. These two-mica granites are characterized by the presence of muscovite and an aluminum saturation index of 1.04–1.13 typical for S-type granite affinity. They display enrichment in LREEs and LILEs, depletion in HFSEs, and weak negative to positive Eu anomalies. The high CaO/Na 2 O ratios and Sr contents, and low Rb contents, together with a comparison with experimental melting results suggest that the two-mica granites were derived through H 2 O-fluxed biotite melting of metagreywacke. The ε Hf (t) values for co-magmatic zircons display a wide range from −11.5 to +1.14, together with heterogeneous ε Hf (t) values (−10.1 to +6.72) for inherited cores implying a mixed source involving ancient sediments and juvenile volcanic materials. Accordingly, the protoliths of the two-mica granites were formed in the forearc setting, and the Late Permian two-mica granites were generated in the subduction environment related to the Paleo-Tethyan Ocean. Our results, along with the occurrence of the Early Paleozoic peraluminous granites in the South Kunlun Belt, suggest that the forearc accretionary complex in the E-KOB underwent multiple anatectic events during continuous subduction and accretion of the oceanic plate.

Petrogenesis and geochemistry of fayalite and fluorite-bearing granite from the Assam Meghalaya Gneissic Complex, West Khasi Hills, Meghalaya, India: their implication towards Rodinia Supercontinent amalgamation

Petrogenesis and geochemistry of fayalite and fluorite-bearing granite from the Assam Meghalaya Gneissic Complex, West Khasi Hills, Meghalaya, India: their implication towards Rodinia Supercontinent amalgamation

New insights into the petrogenesis of the Bozhushan W-Sn mineralization-associated granites, Yunnan province, SW China: Evidence of microgranitoid enclaves

The Bozhushan granites, located in the southeastern Yunnan Province W–Sn polymetallic metallogenic belt in SW China, have considerable W-Sn endowment. However, their petrogenesis remains uncertain, as both crustal and mantle origins have been proposed. Numerous microgranular enclaves (MEs) are found in the Bozhushan granites, and the origin of these MEs can give insights into the petrogenesis of these ore-forming granites. Here we present an integrated study of the major and trace elements, whole-rock Sr–Nd isotopes, and zircon Hf–O isotopes of the MEs. The MEs from the Bozhushan granites are commonly composed of monzodiorite and granodiorite, and they have lower SiO2 (51.7–66.4 wt%) and higher TiO2 (0.83–1.67 wt%), MgO (1.68–4.49 wt%), and CaO (1.74–4.26 wt%) contents than those of their hosts (SiO2 = 64.3–76.9 wt%; TiO2 = 0.4–0.67 wt%; MgO = 0.86–1.33 wt%; CaO = 2.08–3.25 wt%). Furthermore, the chemical compositions of the MEs and host granites are discontinuous and do not show linear trends in element variation diagrams, as might be expected if the MEs represented restites, thus implying disparate genesis. The observed near-linear element variation most probably reflects mixing of mafic and felsic magma end-members in various proportions. In addition, the MEs have Sr–Nd–Hf–O isotopic characteristics (87Sr/86Sri = 0.7117–0.7138, εNd = − 12.59 to − 9.26, εHf(t) = − 13.1 to − 6.1, and δ18O = 8.39‰–9.19‰) and zircon U–Pb ages (87.4 ± 1.0 Ma to 86.5 ± 0.4 Ma) that are similar to those of their host granites. We conclude that the similarity of trace-element contents and Sr–Nd isotopic compositions between the MEs and host granites was caused by diffusion and partial re-equilibration. However, if the magma temperature of the MEs was 850 °C, 950 °C, or 1050 °C, the required Zr contents for zircon saturation would be 238–854 ppm, 497–1785 ppm, or 928–3334 ppm, respectively, which are substantially higher than those measured for the bulk rocks (44–436 ppm). Furthermore, zircons from the MEs have Ti-in-zircon temperatures (Tzr; MEs, 669–884 °C; host, 790–842 °C) and Th/U ratios (MEs, 3.43–8.85; host, 2.68–11.86) that are indistinguishable from those of their host granites. Thus, on the basis of our new data, we propose that the MEs of the Bozhushan granites might have been derived from mantle-derived mafic magma. Zircons from the MEs did not crystallize directly within the MEs but rather were xenocrysts that formed during the early stage of magmatic evolution at the bottom of the granitic magma chamber and were subsequently incorporated into the MEs when mafic magma was injected into the granitic magma chamber. The Hf–O isotopes of zircons in this case cannot be used to constrain the primary composition of the magma that formed the MEs. During the Late Cretaceous, owing to lithospheric extension and asthenospheric underplating, the lower crust was partially melted to form high-temperature (790–842 °C) granitic magma in the Bozhushan area. During the formation of the W–Sn mineralization associated with the Bozhushan granites, 10%–20% underplated mafic magma mixed with granitic magma and contributed both heat and mantle-derived material. Therefore, we consider that the Bozhushan granites are clearly characteristic of A-type granites, but the W–Sn mineralization was formed as a result of high-temperature partial melting of Sn–W-rich metasedimentary sources triggered by additional heat provided by mantle-sourced mafic magma.

Petrogenesis and redox state of late Mesozoic granites in the Pingmiao deposit: Implications for the W–Cu–Mo mineralization in the Dahutang district

The Pingmiao W (Cu) deposit is located in the central part of the newly-discovered giant Dahutang ore-concentrated district, South China. Field relationships and mineral assemblages confirm that the W (Cu) mineralization in the Pingmiao deposit is genetically related to multiphase late Mesozoic granites, which include the porphyritic two-mica granite, biotite granite porphyry, fine-grained muscovite granite, and Li-mica albite granite. Zircon U–Pb dating shows that these granites emplaced at ca. 146–143 Ma, which are coeval with the W–Cu–Mo-bearing granitoids from other ore deposits in the Dahutang district. The strongly peraluminous (A/CNK > 1.1) feature, negative correlations between Rb and Th and between Rb and P2O5, low Zr + Nb + Ce + Y values (mostly lower than 200), and relatively low Zr saturation temperatures (lower than 800 °C) suggest that these granites are typical S-type granite. These granites show similar Nd isotopes (−8.91 to −4.61), CaO/Na2O (0.2–0.57), and Al2O3/TiO2 (mostly ranging of 50–90) ratios with those W–Cu–Mo-bearing granitoids from other ore deposits in the Dahutang district, suggesting that they derived from partial melting of metapelites in the Shuangqiaoshan Group (or the Proterozoic metamorphic basement geochemically similar to the Shuangqiaoshan Group), with involving of minor mafic–ultramafic volcanic rocks. Geochemical fractionation trends recorded by whole-rocks and micas permit to distinguish the evolutionary trend from the porphyritic two-mica granite and biotite granite porphyry to the fine-grained muscovite granite and Li-mica albite granite. The apparent rare earth element tetrad effect, high Li and F contents, low K/Rb, Zr/Hf, and Nb/Ta ratios, as well as the zoned features of micas suggest that the melt–fluid interaction occurring during the formation of Li-mica albite granite. The Pingmiao granites have reduced redox state, revealed by their low whole-rock Fe2O3/FeO ratios (mostly <0.5), biotite Fe3+/Fe2+ ratios (ranging of 0.02–0.07), zircon Ce4+/Ce3+ ratios (median value of 18.70), and oxygen fugacity (near or below the FMQ buffer). The data in this study indicate that the late Mesozoic granitoids in the Dahutang district are favorable for W, Cu (<1 Mt), and Mo (<0.3 Mt) mineralization. Notably, the more evolved Li-mica albite granite has potential for W, Sn, Nb and Ta mineralization.

Petrogenesis of Late Cretaceous granites and implications for W-Sn mineralization in the Youjiang Basin, South China

Five Late Cretaceous tungsten-tin ore clusters (Gejiu, Dulong, Bainiuchang and Dachang tin deposits and Damingshan tungsten deposit) have been identified in the Youjiang Basin, South China. However, litter attention has been paid to such W-Sn metallogenetic specialization in the Youjiang Basin, as well as the geodynamic setting of mineralization and related magmatism. This study presents petrographical, geochronological, zircon Lu-Hf isotopic and whole-rock geochemical analyses for the Kunlunguan (KLG) biotite granites from the Damingshan ore cluster in the eastern part of the Youjiang Basin, and synthesizes previously published data from other ore clusters. The KLG granites yield crystallization ages of ∼ 100.2–98.6 Ma, and are characterized by high SiO2 and low A/CNK, Rb/Sr and 10000*Ga/Al, belonging to metaluminous to weakly peraluminous unfractionated I-type granite. The granites have initial 87Sr/86Sr ranging from 0.70919 to 0.71133 and εNd(t) from −9.3 to −6.8 with zircon εHf(t) ranging from −13.2 to −3.1, Eu/Eu* from 0.18 to 0.42 and Ce/Ce* from 7.43 to 254. Such signatures suggest that the KLG granites originated from partial melting of lower crustal mafic rocks with a minor mantle component. Overall, the W-Sn metallogenic specialization in the Youjiang Basin was first-order controlled by crustal sources of ore-host granites. The metallogenic age of the W-Sn deposits (∼97–75 Ma) is similar to the crystallization age of the granites (∼100–77 Ma), and the ages of mineralization and granites in the west of the Youjiang Basin are relatively younger than those in the east. The Late Cretaceous W-Sn mineralization system in the Youjiang Basin belongs to a part of an EW-trending Sn-W-Cu mineralization belt from Myanmar to Guangdong (South China), forming in an extensional setting caused by the Neo-Tethys oceanic slab roll-back.

Petrogenesis of the granite related to the Baishaziling Sn deposit, Dayishan ore field, Southern China

The Baishaziling greisen-type tin deposit is located in the Dayishan ore field, Nanling Range, Southern China. In this study, for the first time, we present both zircon and cassiterite UPb dating, whole-rock elements, zircon LuHf and apatite Nd isotopic compositions to better constrain the petrogenesis of granite and its genetic link with Sn mineralization. Zircon UPb ages of fine-grained granite and coarse-grained granite are 154 ± 1.8 Ma and 153 ± 2.1 Ma, respectively, which are consistent with the cassiterite UPb dating of 154 ± 5.4 Ma, implying genetic relationship between the Baishaziling granite and tin metallogenesis. The Baishaziling granites exhibit high SiO2, K2O + Na2O, Zr + Nb + Ce + Y contents, low P2O5 and Sr contents, and high ratios of Ga/Al, TFeO/(TFeO + MgO), implying A-type granite affinity with characteristics of high-K calc-alkaline and weakly peraluminous. The zircon εHf(t) values and apatite εNd(t) values of the granite vary from −4.46 to −1.81 and −8.37 to −7.10, with two-stage Hf and Nd model ages of 1.40 to 1.50 Ga and 1.52 to 1.64 Ga, indicating that they were generated by the partial melt of the Proterozoic basement with the involvement of mantle magma. In addition, formation of Dayishan granite was likely associated with an intraplate extensional setting caused by the subduction of the Palaeo-Pacific plate. The Baishaziling reduced granites have high stannum and boron contents, which are in favor of the tin mineralization.

Petrogenesis and tectonic setting of A-type granites in the Babouri-Figuil Magmatic Complex (North Cameroon): Constraints from whole rock geochemistry, zircon U[sbnd]Pb geochronology and Sr-Nd-Hf isotopes

The tectonics of the Central Africa Orogenic Belt (CAOB, in Cameroon, Chad, and the Central Africa Republic) is poorly constrained. For this reason, a study was carried out at the Cameroon-Chad border from biotite granite and hornblende-biotite massifs that intruded a gneiss-amphibolites basement of the NW Cameroon domain. Together, we report data on the whole-rock major and trace element compositions, mineral chemistry, and zircon U/Pb ages, supported by Nd-Sr-Hf isotopes. Both rocks are calc-alkaline, except for one sample with a Rittmann Serial Index (σ) > 3.5 (alkaline), high-K, and marginally peraluminous. The biotite granite is alkalic-calcic, whereas hornblende-biotite granite is alkalic. These rocks are characterized by high contents in SiO2 (> 69.85 wt%), Fe-number [FeOt/(FeOt+MgO)] (ferroan), TiO2/MgO, and low CaO, MgO, and P2O5 contents. Their petrological and geochemical features, such as early formed sodic and iron-rich amphibole, late crystallized biotite, and high Ga/Al ratios, are consistent with A-type granite formed from F and Cl enriched melts. Biotites compositions are close to those of annite, and amphiboles to ferro-amphibole, ferro-edenite, and ferro-gedrite types. The correlation for some major elements against SiO2 is consistent with fractionation of K-feldspar, plagioclase, apatite, amphibole, biotite, FeTi oxides, and MnO-rich phases under 882 to 967 °C, < 5 kb, and low ƒO2 (∆QFM = −0.55) at shallow crustal levels between <1 and 7 Km. Zircon U/Pb geochronology indicates two magmatic episodes for the biotite granite (RBO-27 and SMO-8) 602 ± 1.6 Ma, 602 ± 1.8 Ma, and (DBE-9) 707 ± 2.5, whereas hornblende-biotite granite (HRI-23) yielded 604 ± 1.0 Ma, respectively. The younger group yielded moderately to notably depleted initial Hf and Nd values [εHf(t) = − 3.4 to +1.8, av. = − 1.80; εNd(t) = − 2.46 to - 0.95, at 1.34 to 1.51 Ga], and low to moderate calculated initial Sr values (87Sr/86Sr(i) = 0.66781–0.70287). The older A-type granite yielded highly depleted initial Hf values (εHf(t) = + 7.74 to +9.30). The strong positive Pb anomaly for these granites indicates involvement of either crustal component or melt from the subducted slab. Given that the obtained initial Hf and Nd values are enriched relative to the depleted mantle (εHf(t) ~ +14; εNd(t) ~ +6.5), it therefore, suggest that these granites could be derived from low-degree partial melting of a juvenile crust extracted from the mantle.

Zircon U–Pb chronology and Hf isotopes of the Lebowa Granite Suite and petrogenesis of the Bushveld Complex, South Africa

Zircon U–Pb chronology and Hf isotopes of the Lebowa Granite Suite and petrogenesis of the Bushveld Complex, South Africa

Triassic tungsten mineralization in Nanling metallogenic belt: A case study of the Zanshi tungsten deposit in the Yajiangqiao area, eastern Hunan Province, China

The Nanling metallogenic belt is rich in critical metal minerals, e.g., tungsten, tin, and rare earth element (REE). The newly discovered Zanshi tungsten deposit, located at the northeastern part of the Nanling metallogenic belt, has drawn great attention from geologists for its rare Triassic magmatic-hydrothermal event in this region. Based on detailed field work, a series of geochemical and geochronological analyses, including whole-rock geochemical analyses consisting of major and trace elements, LA-ICP-MS monazite U-Pb dating of the granites and quartz Rb-Sr and muscovite 40Ar-39Ar isotopic dating of the ore-bearing quartz veins, were carried out in this study, aiming to constrain the rock- and ore-forming ages of the deposit as well as the petrogenesis of granites. The whole-rock geochemical analyses, the medium to fine-grained two-mica monzonitic granites in the Zanshi tungsten deposit are peraluminous S-type granites and derived from the partial melting of metamorphic graywackes in a post-collisional extensional tectonic setting. The LA-ICP-MS monazite U-Pb dating on the two medium- to fine-grained two-mica monzonitic granite samples yields weighted average ages of 218.2 ± 1.2 Ma (MSWD = 1.3) and 221.7 ± 1.7 Ma (MSWD = 2.7), respectively. These ages are consistent with the quartz Rb-Sr and muscovite 40Ar-39Ar isotopic ages of the ore-bearing quartz veins, which are 218.7 ± 3.2 Ma and 215.1 ± 2.0 Ma, respectively, revealing that the tungsten mineralization in this deposit is related to the Triassic magmatic-hydrothermal activity. Combined with previous studies, the Zanshi tungsten deposit likely experienced about 5 M.y. of magmatic evolution and 3.6 M.y. of mineralization. Meanwhile, the cooling rate of the ore-forming fluids of this deposit was about 111 °C/M.y., which may be regarded as a controlling factor which affects the ore grade of the deposit.

Petrogenesis of high-maficity S-type granites: Insight from the early Paleozoic Jinxi granite, South China

Experimental S-type melts are characterized by high silica (SiO2 > 70 wt%) and low-maficity (FeOT + MgO < 4 wt%) natures. However, more and more studies revealed that many natural S-type granites exhibited chemical compositions differing from the experimental melts, these S-type granites have relatively low SiO2 but high FeOT + MgO contents. Several models have been proposed for their petrogenesis: magma mixing, source heterogeneity, entrainment of metamorphic garnets, crystal accumulation, etc. In this study, we carried out integrated petrological and mineralogical researches on the early Paleozoic Jinxi granites (ca. 442 Ma) in the Cathaysia Block, South China. They are strongly peraluminous (average A/CNK = 1.31), K-rich (average K2O/Na2O = 1.50) S-type granites, and can be divided into high-maficity (FeOT + MgO > 4%) and low-maficity types (FeOT + MgO < 4%). A combing of field, petrological, and lithochemical evidence indicates that the Jinxi granites did not undergo magma mixing process, and they were derived from ancient crustal rocks without the input of mantle-derived ferromagnesian components, ruling out the mixing model. Both the high-maficity and low-maficity samples of the Jinxi granites show whole-rock Sr-Nd and zircon Hf-O isotopic characteristics indicating a metasedimentary origin, precluding the mafic meta-igneous source. The metasedimentary origin is also supported by the evidence of inherited zircons, whole-rock geochemistry and field observation. Melt extraction and crystal accumulation seem unlikely due to the absences of a prominent silica gap and the complementary geochemical relationship between the high-maficity and low-maficity granites. Furthermore, the absences of metamorphic garnets and significant positive correlations of FeOT + MgO vs. Y, Yb, and A/CNK, argue against the metamorphic garnet entrainment model. The biotites with a very high proportion (up to ~25%) are observed in the high-maficity granites, indicating that these biotites are not all magmatic biotites. It is supported by their occurrences and compositions. Given that the Jinxi granites formed via biotite fluid-absent melting at ~828 °C and ~ 5 kbar, remnant reactant biotites and potential peritectic biotites should be high-temperature and Ti-rich, which differs from the Ti-poor characteristic of the biotites in the Jinxi high-maficity granites. Moreover, highly variable whole-rock chemistry, particularly Na:K ratios, and petrographic observations suggest that the Jinxi granites have been modified by late- to post-magmatic processes involving introduction of alkalis and H2O during cooling. These features suggest the partial replacement of early magmatic garnet by biotite, and plenty of secondary biotites formed in post-magmatic metamorphism and alteration, which leads to a high proportion of biotite, and thus high FeOT + MgO contents in the Jinxi high-maficity granites. In this case, the effect of late- to post-magmatic processes should be noticed in the study on high-maficity S-type granites.

Petrogenesis and geodynamic setting of the Late Jurassic Queshan adakitic granite, Jiaodong Peninsula, southeastern North China Craton: Zircon U–Pb geochronological, geochemical, and Lu–Hf isotopic evidence

Late Mesozoic granites are present throughout the Jiaodong Peninsula in eastern China, but the petrogenesis of these granites, the magma sources, and the geodynamic setting of the magmatism remain unclear. This paper presents new zircon U–Pb geochronological and Lu–Hf isotopic and whole‐rock geochemical data for the Late Jurassic Queshan pluton in the Shandong Peninsula, an area that represents the boundary between the Jiaobei and Sulu ultrahigh‐pressure (UHP) terranes. Laser ablation–inductively coupled plasma–mass spectrometry zircon U–Pb dating yields Late Jurassic ages from 158 ± 1 to 153 ± 1 Ma for the pluton in addition to a small number of inherited zircons that yield ages that cluster at 2410, 1831–1776, 750, and 209–202 Ma. Zircons from different samples have similar 176Hf/177Hf values (0.281926–0.282255) and variably negative εHf (t) values that range from −26.5 to −15.1 (weighted mean of −22.9 ± 0.9). The corresponding two‐stage Hf model ages range from 2,869 to 2,154 Ma, with a weighted mean value of 2,645 ± 54 Ma. These data indicate that the magmas that formed the Queshan pluton were derived from multiple sources, including the lower crust of the North China (NCC) and Yangtze (YC) cratons, as well as collision‐related alkaline rocks. The whole‐rock geochemical compositions of the samples indicate that the granites are weakly peraluminous, are high‐K and calc‐alkaline with I‐type affinities, and have high contents of Sr, low contents of Y and Yb, high (La/Yb)N and Sr/Y values, and positive Eu anomalies (δEu = 1.20–1.65), indicating an adakitic affinity. This indicates that the Queshan granites formed from magmas generated by partial melting of a thickened region of the crust (&gt;50 km) associated with eclogite, garnet amphibolite, or amphibolite residual material. The genesis of the Late Jurassic granites are also likely to have been influenced by the collisional orogeny between the NCC and YC and continued subduction of the Izanagi Plate. Thickening of the lower crust associated with this continental collisional event occurred before the magmatism, with further compression and thickening of the lower crust caused by the low‐angle subduction of the Izanagi Plate beneath northeastern China being the main geodynamic driver of the formation of the granites in this region.

Petrogenesis and tectonic setting of the late Early Cretaceous Kong Co A-type granite in the northern margin of Central Lhasa Subterrane, Tibet

在中拉萨地块北部尼玛控错地区发育着一套碱性长石花岗岩，对该花岗岩体开展成因和形成背景的研究，能为探索班公湖-怒江洋的构造演化提供有价值的信息。用LA-ICP-MS方法测得该花岗岩的锆石²⁰⁶Pb/²³⁸U年龄加权平均值为104.9±1.4Ma （MSWD=1.5）和104.6±1.3Ma （MSWD=1.3），表明该岩体形成于早白垩世。花岗岩具有高硅（SiO₂=76.75%~77.51%，平均77.27%）、高钾（K₂O=4.61%~4.85%，平均4.77%）、高碱（K₂O+Na₂O=8.24%~8.57%，平均8.44%）、低钙（CaO=0.28%~0.48%，平均0.35%）、低镁（MgO=0.11%~0.16%，平均0.13%）和低铝（Al₂O₃=11.79%~12.22%，平均12.09%）等特征，里特曼指数（σ）为1.96~2.15（平均2.08），A/NK值为1.06~1.09，A/CNK值为1.01~1.04。这些特征表明控错花岗岩为弱过铝质的高钾钙碱性-钾玄岩系列岩石。控错花岗岩相对富集Zr、Nb、Ce、Y和Hf等微量元素，相对亏损Ti、Ba、Sr和P等微量元素，分异系数（DI）为95.5~96.9（平均：96.3），还具有较高的FeO^T/MgO值（5.61~10.22，平均7.26）、10000Ga/Al值（2.78~2.56，平均2.84）、Y/Nb值（2.29~4.97，平均3.57）、Rb/Nb值（11.6~18.2，平均15.2）；此外，该岩体还具有较高的全岩Zr饱和温度（875~910℃，平均890℃）和锆石Ti饱和温度（848~919℃，平均890℃），明显的Eu负异常（δEu=0.04~0.09，平均0.06），以及向右缓倾的Ⅴ型稀土元素配分曲线，这些特征表明控错花岗岩为产于碰撞后环境的A2型花岗岩。正的锆石ε_Hf（t）值（4.26~6.38，平均5.16）、相对年轻的锆石Hf地壳模式年龄（t_DM2=757~889Ma，平均833Ma）、下地壳与地幔混合特征的（⁸⁷Sr/⁸⁶Sr）_t（0.7194~0.7407，平均0.7313）、ε_Nd（t）（-3.39~-3.00，平均-3.24））和Pb同位素特征（（²⁰⁶Pb/²⁰⁴Pb）_t=18.792~18.845，（²⁰⁷Pb/²⁰⁴Pb）_t=15.708~15.718，（²⁰⁸Pb/²⁰⁴Pb）_t=38.870~38.037），指示控错花岗岩熔融于幔源物质加入的新生地壳。研究结果揭示，控错花岗岩形成于羌塘-拉萨地块碰撞作用下，俯冲板片的断离后，软流圈上涌诱发的地壳部分熔融，并经历了显著的以钾长石和角闪石为主的分离结晶作用。;A set of alkali feldspar granite develops well in the Kong Co of Nyima County in the northern margin of Central Lhasa Subterrane, Tibet, which can provide invaluable information to explore the geological evolution of the Bangong Co-Nujiang Ocean. The weighted averaged zircon ²⁰⁶Pb/²³⁸U ages of the granite measured by LA-ICP-MS are 104.9±1.4Ma (MSWD=1.5) and 104.6±1.3Ma (MSWD=1.3), respectively, indicating that it was formed in the late phase of Early Cretaceous magmatism. The rocks in Kong Co granite are grayish-white, with fine-grained equigranular structure and medium coarse-grained porphyritic-like texture. The rock-forming minerals mainly include quartz, potassium feldspar, plagioclase, and a small amount of transparent accessory minerals such as biotite and amphibole, as well as a few melanocratic mineral like magnetite. The granite is characterized by high contents of SiO₂ (6.75%~77.51%), K₂O (4.61%~4.85%), and K₂O+Na₂O (8.24%~8.57%), with low contents of CaO (0.28%~0.48%), MgO (0.11%~0.16%) and Al₂O₃ (11.79%~12.22%), and a Rittman index (σ₄₃) of 1.96~2.15 and A/CNK ratios of 1.01~1.04. These characteristics reveal that the Kong Co granite is weakly peraluminous high potassium calc-alkaline-potassium basalt series rock. The granite is relatively enriched in Zr, Nb, Ce, Y and Hf, and deficient in Ti, Ba, Sr and P. It shows a highly variation of index (DI:95.50~96.90), and also has high values of FeO^T/MgO (5.61~10.22), 10000Ga/Al (2.78~2.56), Y/Nb (2.29~4.97), Y/Nb (2.29~4.97), Rb/Nb (11.6~18.2), which is consistent with A2-type granites produced in post collision environment. In addition, the rock has high whole-rock Zr saturation temperatures (875~910℃) and zircon Ti saturation temperatures (848~919℃), with a significant negative Eu anomaly (δEu=0.04~0.09), and a Ⅴ-shaped rare earth element curve gently inclined to the right. These characteristics also prove the Kong Co granite is A2 type granite. They have relatively positive ε_Hf(t) values (4.26~6.38), and two-stage Hf model ages (t_DM2) ranging from 757Ma to 889Ma, with (⁸⁷Sr/⁸⁶Sr)_t=0.7194~0.7407 and ε_Nd(t)=-3.39~-3.00, and Pb isotopic ((²⁰⁶Pb/²⁰⁴Pb)_t=18.792~18.845, (²⁰⁷Pb/²⁰⁴Pb)_t=15.708~15.718, (²⁰⁸Pb/²⁰⁴Pb)_t=38.870~38.037) characteristics of lower crust-mantle mixture. These data indicate that the granite was sourced from interaction between mantle-derived and juvenile lower crust-derived melts. This occurred when the post collision extension of Qiangtang and Lhasa terranes the subduction plate split to create a slab window, and rising asthenosphere triggered re-melting of the lower crust basalt, resulting in the formation of the late Early Cretaceous A-type granite around Kong Co.

Odyssey of Crustal Maturation During Early History of the Earth: An Insight from Petrogenesis of Distinct Mesoarchean and Neoarchean Granite and Trondhjemite Suites from Western Margin of Dharwar Craton (India)

Odyssey of Crustal Maturation During Early History of the Earth: An Insight from Petrogenesis of Distinct Mesoarchean and Neoarchean Granite and Trondhjemite Suites from Western Margin of Dharwar Craton (India)

Preferential dissolution of uranium-rich zircon can bias the hafnium isotope compositions of granites

Abstract Hafnium (Hf) isotopes in zircon are important tracers of granite petrogenesis and continental crust evolution. However, zircon in granites generally shows large Hf isotope variations, and the reasons for this are debated. We applied U-Pb geochronology, trace-element, and Hf isotope analyses of zircon from the Miocene Himalayan granites to address this issue. Autocrystic zircon had εHf values (at 20 Ma) of–12.0 to–4.3 (median =–9). Inherited zircon yielded εHf values (at 20 Ma) of–34.8 to +0.3 (median =–13); the majority of εHf values were lower than those of autocrystic zircon. The εHf values of inherited zircon with high U concentrations resembled those of autocrystic zircon. Geochemical data indicates that the granites were generated during relatively low-temperature (&amp;lt;800 °C) partial melting of metasedimentary rocks, which, coupled with kinetic hindrance, may have led to the preferential dissolution of high-U zircon that could dissolve more efficiently into anatectic melt due to higher amounts of radiation damage. Consequently, Hf values of autocrystic zircon can be biased toward the values of U-rich zircon in the source. By contrast, literature data indicate that granites generated at high temperatures (&amp;gt;820–850 °C) generally contain autocrystic and inherited zircons with comparable Hf isotope values. During higher-temperature melting, indiscriminate dissolution of source zircon until saturation is reached will result in near-complete inheritance of Hf isotope ratios from the source. Our results impose an extra layer of complexity to interpretation of the zircon Hf isotope archive that is not currently considered.

Petrogenesis of Paleoproterozoic alkali-feldspar granites associated with alkaline rocks from the Trans-North China Orogen

Granitoids are the dominant component of the continental crust and can be used as probes for crustal formation and evolution. The origin of granites, especially ambiguous granites with alkaline affinities emplaced in orogenic settings, however, remains controversial. Here, we report the petrology, geochronology and geochemistry of Paleoproterozoic alkali-feldspar granites associated with carbonated alkaline rocks from the Trans-North China Orogen in the North China Craton. Corundum-bearing Al-rich gneisses are associated with the granites and occasionally contain granite pockets and veinlets. The rocks have high amounts of K2O (10–14 wt%) and low CaO (0.3–2.3 wt%) contents and show metaluminous to weakly peraluminous features. Moreover, they have low levels of total REE (18–100 ppm) and show strong LREE enrichment [(La/Yb)CN = 44–128] and positive Eu anomalies (δEu = 1.6–10.2). The zircons record a U–Pb age of 1809 ± 3 Ma and εHf(t) values ranging from −3.7 to −7.1, which are consistent with those in the gneisses (1827 ± 14 Ma, εHf(t) = −3.3 to −8.4). Inherited zircons occur in both rocks and show similar ages of ∼2.0 and ∼2.1 Ga. Considerably high δ18OSMOW ratios (9.9–10.9 ‰) in the zircons and low εNd(t) values (−4.0 to −6.2) of the granites were identified. The granite was generated by partial melting of pelitic rocks instead of differentiation of mantle-derived magmas, whilst the gneiss represents the residuum. The carbonated alkaline magmas arising from the mantle provided sufficient heat for anatexis of the crust. Granitoid rocks showing alkaline affinity in orogenic belts may not be the fractionation products of mantle-derived melts but may have formed from reworked sedimentary materials.

Early Paleozoic Adakitic Granitoids from the Xingshuping Gold Deposit of East Qinling, China: Petrogenesis and Tectonic Significance

This study discussed the pertrological classification, geochronology, petrogenesis and tectonic evolution of early Paleozoic granites from the Xingshuping gold deposit in the East Qinling orogenic belt. In order to achieve this target, we carried out an integrated study of zircon U–Pb age, whole-rock major and trace elements, as well as Sr–Nd–Hf isotope compositions for the Xingshuping granites (part of the Wuduoshan pluton) from the Erlangping unit. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U–Pb dating constrains the emplacement age of the Xingshuping granites at 446.2 ± 1.2 Ma. The rocks at Xingshuping can be divided into two types: mainly biotite granite and monzonitic granite. The biotite granites are typical adakitic rocks, while the monzonitic granites show characteristics similar to normal arc volcanic rocks. The geochemical compositions reveal that they were derived from a clay-rich, plagioclase-rich and biotite-rich psammitic lower continental crust source, with contributions of mantle-derived magmas. The distinction is that the biotite granites were primarily derived from partial melting in a syn-collision extension setting, whereas the monzonitic granite went through a fractional crystallization process in an intraplate anorogenic setting.

Comparison of Granitoid Characteristics West Kalimantan and Karangsambung Based On Mineralogical And Geochemical Aspects

Indonesia was included in the ring of fire so that it has various types of tectonic products, one of which is granitoid. Granitoid is very complex rock and many are found in Indonesia. Some of them are found in West Kalimantan and Karangsambung. Basis of the reasearch is there is no research that compares granitoid in two regions. The purpose of this study was to compare rock characteristics and granite petrogenesis of West Kalimantan and Karangsambung. The research method used was collecting data on field, also laboratory analysis of rock samples using a polarization microscope, refraction microscope, and X-Ray Fluorescence analysis. The mineralogical characteristics of each study area tend to be almost the same. The predominant composition of the main minerals is quartz, plagioclase and orthoclase. But specifically the rock samples from West Kalimantan have been altered from phylic-silicification-propylitic. The entire study area contained accessory minerals, namely apatite, zircon, titanite, and for monazite only in the West Kalimantan sample. There was mineralization up to the supergene stage in the presence of the characteristic minerals for the supergene covelite and chalcocytes in the West Kalimantan sample. Geochemical analysis of both regions shows the same magma affinity, namely Calc Alkaline - High K Calc Alkaline. For West Kalimantan, the value of A / CNK &lt;1.1 has a type metaluminious and &gt; 1.1 a type peraluminious. Meanwhile, Karangsambung A / CNK value &lt;1.1 has a type metaluminious. So that West Kalimantan granite has two I-type and S-type. While Karangsambung is I-type. West Kalimantan granite is formed in continental arc granite (CAG) and continental collision granite (CCG). Meanwhile, Karangsambung in Volcanic Arc Granite (VAG). It can be concluded that the granites of the two regions have quite different characteristics even though they belong to a relatively similar tectonic environment.

Understanding pre- and syn-orogenic tectonic evolution in western Himalaya through age and petrogenesis of Palaeozoic and Cenozoic granites from upper structural levels of Bhagirathi Valley, NW India

AbstractThe Himalaya is characterized by the presence of both pre-Himalayan Palaeozoic and syn-Himalayan Cenozoic granitic bodies, which can help unravel the pre- to syn-collisional geodynamics of this orogen. In the Bhagirathi Valley of Western Himalaya, such granites and the Tethyan Himalayan Sequence (THS) hosting them are bound to the south by the top-to-the-N extensional Jhala Normal Fault (JNF) and low-grade metapelite of the THS to its north. The THS is intruded by a set of leucocratic dykes concordant to the JNF. Zircon U–Pb laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) geochronology of the THS and one leucocratic dyke reveals that the two rocks have a strikingly similar age distribution, with a common and most prominent age peak at ~1000 Ma. To the north of the THS lies Bhaironghati Granite, a Palaeozoic two-mica granite, which shows a crystallization age of 512.28 ± 1.58 Ma. Our geochemical analysis indicates that it is a product of pre-Himalayan Palaeozoic magmatism owing to extensional tectonics in a back-arc or rift setting following the assembly of Gondwana (500–530 Ma). The Cenozoic Gangotri Leucogranite lies to the north of Bhaironghati Granite, and U–Pb dating of zircon from this leucogranite gives a crystallization age of 21.73 ± 0.11 Ma. Our geochemical studies suggest that the Gangotri Leucogranite is a product of muscovite-dehydration melting of the lower crust owing to flexural bending in relation to steepening of the subducted Indian plate. The leucocratic dykes are highly refracted parts of the Gangotri Leucogranite that migrated and emplaced along extensional fault zones related to the JNF and scavenged zircon from the host THS during crystallization.